1. Field of the Invention
The invention relates to rock crushers such as cone or jaw crushers and, more particularly, relates to a rock crusher having inserts disposed on at least one crushing surface thereof for enhanced crushing action, enhanced wear resistance, enhanced capacity, and reduced power requirements. The invention additionally relates to a method of fabricating a wear liner having such inserts and to an improved method of crushing rock.
2. Discussion of the Related Art
Rock crushers have been used for centuries in quarry operations and the like to break large pieces of material, such as rock, stone and the like (hereinafter "rock"), into smaller pieces more suitable for applications such as road paving. There are many types of rock crushers including: cone crushers (also known as gyratory crushers), jaw crushers, impactors, hammermills, and pulverizers to name a few.
Cone or gyratory crushers include an eccentrically gyratory conical head, an opposed bowl, and a crushing cavity or crushing chamber formed between the head and the bowl. Rock that falls into the crushing chamber is crushed by compression to a smaller size generally consistent with the size of the gap in the crushing cavity at the point at which the rock is struck. The average size of the stone formed from the crushing operation can be changed by adjusting the minimum gap between the bowl and the head, which minimum gap is known in the art as "the closed side setting." For a more detailed description of the operation of a cone crusher is desired, reference may be had to U.S. Pat. No. 3,750,967 to DeDiemar et al., entitled "Gyratory Crusher Having Interchangeable Head Mantles," issued Aug. 7, 1973 and assigned to an assignee common with the present invention (hereinafter incorporated by reference).
A jaw crusher includes opposed generally rectangular dies, one of which is swingably movable relatively toward and away from the other to crush rock therebetween. For a more detailed description of the operation of a jaw crusher, see U.S. Pat. No. 3,804,345 to DeDiemer, entitled "Jaw Crusher Die Mounting," issued Apr. 16, 1979, and assigned to an assignee common with the present invention (hereinafter incorporated by reference).
The crushing surfaces of both cone crushers and jaw crushers suffer from severe and relatively rapid wear due to abrasive contact with the stone being crushed. In order to ameliorate this wear, both cone crushers and jaw crushers typically utilize as one and usually both crushing surfaces a replaceable hardened, wear-resistant manganese wear liner. A jaw crusher incorporating replaceable manganese wear liners is disclosed, for example, in U.S. Pat. No. 2,828,925 to Rumpel. A gyratory or cone crusher incorporating replaceable manganese wear liners is disclosed, for example, in the DeDiemer '967 patent.
While manganese wear liners serve to increase the useful life of the crushing elements of a crusher, they are not a cure-all for all of a crusher's problems.
For instance, manganese wear liners still exhibit relatively rapid and uneven wear, particularly when subject to contact with an abrasive material such as sandstone. They therefore must be replaced relatively frequently--on the order of every 10 days to 3 weeks in the case of a cone crusher crushing sandstone. The manganese wear liners are relatively expensive, and their replacement requires several hours of down time. Frequent replacements of wear liners therefore can be quite costly.
Another problem that is associated with conventional crushers and that is not solved by traditional wear liners is that their crushing action does not consistently produce a product of sufficiently high cubicity. Cubicity is defined as the ratio of length to width to thickness of a sample particle. For instance, a particle having a length of 4", a width of 2", and a thickness of 1" has a 4:2:1 cubicity ratio. Many industries, and particularly the paving industry, increasingly are requiring the production of gravel or other paving materials of consistent, relatively high cubicity. This need is particularly evident in the case of materials designed for use in so-called "super paving" projects in which state highway departments require that no more than 15% of the crushed rock used in the paving materials may have a cubicity ratio of greater than 3:1:1. Operators of most cone and jaw crushers (the crushers most commonly used to produce materials for the paving industry) sometimes find it exceedingly difficult to meet these cubicity requirements, particularly if the materials being crushed are shale-like or otherwise tend to shatter into long, flat pieces. Crushed product failing to meet the cubicity requirements cannot be screened or otherwise improved to meet these requirements and hence must be rejected. As a result, it is not uncommon for a state highway department to reject several hundred thousand tons of rock produced for use in a super paving project.
The industry has recently addressed the cubicity problem and solved it to a limited extent by increasing the stroke and speed of crushing machines. For instance, crushed rock produced by the Telsmith H-Series crusher exhibits improved cubicity when compared to materials produced by other, earlier crushers. However, meeting cubicity requirements for super paving projects is often difficult even with these modern crushers, particularly when the rock is inherently relatively non-cubic, i.e., it tends to break into long, flat pieces.
Proposals have been made to incorporate inserts into a crushing surface of a crusher. For instance, U.S. Pat. No. 201,187 to Markel and U.S. Pat. No. 273,477 to Dodge both disclose jaw crushers having replaceable pins or points that are designed to absorb the abrasive action of the stone being crushed and hence to form the wear surface of the crusher. Replacement of these pins or points apparently was considered to be a more attractive option than replacing an entire die or even an entire liner of a crusher. U.S. Pat. No. 883,619 to Canda simnilarly discloses the use of hardened steel ribs which are connected to the dies of the jaws and which form the wear elements of the crusher.
Proposals have also been made to insert elements into the crushing surface of a jaw crusher to enhance its crushing ability. For instance, U.S. Pat. No. 1,513,855 to Phelps proposes the incorporation of differently-sized crushing and cutting teeth into the facing dies to give the machine increased capacity. Similarly, U.S. Pat. No. 3,241,777 to Kuntz proposes the attachment of hardened steel balls to the opposed dies of a jaw crusher to act as a wear surface. The balls are independently and separately mounted so that the resistance to abrasion of the cutting surface can be varied as desired to provide an optimum crushing surface for a particular material or operation.
None of the prior art patents discussed above disclose the combination of protruding inserts and a manganese wear liner in a jaw or cone crusher. Moreover, none of these patents discuss cubicity.
What is needed therefore are a method and apparatus which add life to the crushing surfaces of a crusher, which increase the cubicity of the crushed material, and which increase the efficiency of the crusher.